1. Field of the Invention
The present invention relates to an optical disk apparatus and a pickup unit and, in particular, to an optical disk apparatus and a pickup unit capable of supporting an optical disk including a plurality of signal layers.
2. Description of the Related Art
In recent years, the use of optical disk apparatuses has become widespread (refer to, for example, Japanese Patent No. 3438160 and Japanese Unexamined Patent Application Publication No. 2004-281026).
To detect a tracking error in an optical disk apparatus, Japanese Patent No. 3438160, for example, describes a one spot push-pull method. The one spot push-pull method is simple and has an advantage over a three-beam method in that the utilization efficiency of a laser beam is high. Therefore, the one spot push-pull method is suitable for recordable optical disk apparatuses.